Valorization of persimmon calyx waste for 2,3-butanediol production by Klebsiella aerogenes with improved sugar recovery and reduced solid loss

Within the framework of a circular bioeconomy, sustainable 2,3-butanediol (2,3-BDO) production technology via a biorefinery process has attracted significant attention. Persimmon calyx waste (PCW) occurs in large quantities during fruit processing stages but has not been investigated as a biorefinery feedstock. This study aimed to evaluate the potential of PCW as a novel feedstock for 2,3-BDO production. By modeling and optimizing an alkali pretreatment process for PCW, the cellulose and hemicellulose contents were significantly improved from 15.71% to 27.00% and from 15.96% to 31.88%, respectively, with minimized solid loss: biomass loading, 149.998 g/L; alkali concentration, 7.500%; treatment temperature, 73.494 °C; and treatment time, 1.000 h. Lignin was significantly reduced from 26.93% to 3.67%, which significantly enhanced the enzymatic digestibility of cellulose (3.8-fold) and hemicellulose (1.6-fold) of pretreated PCW (ptPCW). Klebsiella aerogenes , a major 2,3-BDO producer capable of metabolizing glucose, xylose, and arabinose, produced about 3.45 g/L of 2,3-BDO within 8 h in ptPCW hydrolysate medium (7.94 g/L sugars with glucose, xylose, and arabinose), which was a superior fermentation performance to the control medium. The fermentation profiles suggested the presence of an additional carbon source that had a positive effect on the improvement of 2,3-BDO production. This study concluded that PCW has a high potential as a novel feedstock for 2,3-BDO production.